Copper alloys

ABSTRACT

Two copper alloys are provided. The first copper alloy may have a composition in the range of from 0.2 to 0.6 wt % chromium, from 0.005 to 0.25 wt % silver, and the balance copper. The second copper alloy may have a composition in the range of from 0.2 to 0.6 wt % chromium, from 0.01 to 0.12 wt % magnesium, and the balance copper. The copper alloys of the present invention may also include zirconium to provide additional softening resistance. These copper alloys can easily be drawn or rolled to fine and ultra fine sizes (0.010 inch and smaller) to be used as a single end wire and constructions made therefrom.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The benefit of U.S. Provisional Patent Application Ser. No. 60/720,990,entitled COPPEER ALLOYS, filed Sep. 27, 2005, is hereby claimed.

BACKGROUND OF THE INVENTION

The present invention relates to two copper alloys containing chromiumand silver or chromium and magnesium and to a process of manufacturingfine wire less than 0.010 inches in diameter.

Copper and its alloys are the principal material used as conductors.Copper alloys are used where the properties of unalloyed copper areinsufficient. ASTM B624 describes a set of properties for one of theseapplications. ASTM B624 specifies the properties of a useful conductoralloy as follows: tensile strength of at least 60 ksi; minimumelectrical conductivity of 85% IACS; and minimum elongation 7% to 9%depending on diameter, such as 8% elongation for a 0.010 inchesdiameter. These properties have been established based on theperformance of an existing alloy, C18135. In addition to theabove-mentioned properties, other characteristics such a softeningresistance and flex life are important factors and must be considered.

The original alloy meeting the requirements of ASTM B624 is copper alloy18135 with a nominal composition of 0.4 wt % cadmium, 0.4 wt % chromium,and balance copper. Due to the hazardous nature of cadmium, search hasbeen ongoing for a replacement for this alloy. Acopper-chromium-zirconium alloy sold under the trade name PERCON 24 hasbeen introduced and has been able to exceed the requirements of ASTMB624. Although this Cu—Cr—Zr alloy has been commercially available,casting and manufacture of alloys containing zirconium is quite complex.Therefore, it would be beneficial to conceive a new alloy which meetsthe requirements of ASTM B624 without hazardous cadmium and difficult toadd zirconium.

The Copper Development Association (CDA) lists several copper alloyscontaining chromium. Copper chromium alloys C182 and 184 contain up to1.2% chromium. Copper chromium alloys are precipitation hardeningalloys. Chromium must be first dissolved in the copper matrix (solidsolution) in order to take advantage of the strengthening effect ofchromium. Following a solid solution treatment, a precipitationhardening alloy undergoes a heat treatment to produce fine particles tostrengthen the alloy. The maximum amount of chromium soluble in copperis 0.65% and that is at 1076 degrees Centigrade where the alloy startsto melt. Practically, the maximum amount of chromium soluble in copperis less than 0.65%. Excess amount of chromium, beyond what has beendissolved in the copper matrix, will remain as large particles (5-10micron or larger) and will not contribute to the strength of the alloy.The large chromium particles may not have an adverse effect for largerdiameter wire (greater than 0.020 inches). However, the large particlesin a conductor, where the single end wire is typically from 0.003 to0.005 inches, and may be down to 0.001 inches or even smaller, willcause wire breaks, a major impediment. Therefore, the amount of chromiumin a copper chromium alloy suitable for conductor applications wheretypical single end wire diameters are 0.001 to 0.010 inches must belimited to less than 0.65%. In fact, the maximum amount of chromiumwhich can be practically dissolved in copper is about 0.5%.

Although a copper-chromium alloy could provide high strength, itssoftening resistance would not be acceptable and measures to improve thesoftening resistance are necessary. Silver, magnesium, and zirconium areknown to improve the softening resistance of copper alloys. Zirconium isone of the most effective elements for increasing the softeningresistance of copper. Zirconium, however, is a highly reactive elementand its addition to copper requires special equipment and techniques.Silver, on the other hand, is an effective element for increasingsoftening resistance of copper and it is quite easy to add to the copperalloy. An additional advantage of silver is that it does not adverselyaffect electrical conductivity. Alloy C107 is an example of a silverbearing copper with improved softening resistance relative to alloyC102. Only a small addition of silver is needed to effect the increasein softening resistance. Additions of more than 0.2% silver, althoughnot harmful, would be a waste of a relatively expensive element.

CDA alloy C18500 describes a copper-chromium-silver alloy. Due to a lackof interest, this alloy has been abandoned since 1992 and has beenremoved from the list of current copper alloys. C18500 contained 0.4 to1.0% chromium and 0.08 to 0.12% silver. Although the high chromium inthis alloy may not be detrimental in large diameter wire and rod, itwill interfere in drawing fine and ultra fine wire of interest (wiretypically smaller than 0.010 inch). In fact, the minimum amount ofchromium listed for C18500 is the optimum amount of chromium needed forthe alloy of the present invention. Silver is a relatively expensiveelement and it must be limited to the amount required to improvesoftening resistance. The nominal amount specified in C18500 is 0.1%.

As an alternative, magnesium may also be added to copper chromium toimprove the softening resistance of the alloy. Since the addition ofmagnesium to copper results in the reduction of electrical conductivity,the amount of added magnesium must be limited to the minimum requiredfor improved softening resistance. For this reason, the amount ofmagnesium must be limited to 0.1%.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided two copperalloys which can be drawn into fine and ultra fine wires (wirestypically smaller than 0.010 inch).

The first copper alloy may have a composition consisting essentially offrom 0.2 to 0.6 wt % chromium, from 0.005 to 0.25 wt % silver, up to0.015 wt % zirconium, and the balance copper.

The second copper alloy may have a composition consisting essentially offrom 0.2 to 0.6 wt % chromium, from 0.01 to 0.12 wt % magnesium, up to0.015 wt % zirconium, and the balance copper.

The present invention also relates to a process of manufacturing acopper alloy wire. The process broadly comprises the steps of providinga copper alloy material containing chromium, subjecting said copperalloy material to a solutionizing treatment to solutionize a majority ofsaid chromium, rapidly quenching said copper alloy material after saidsolutionizing treatment to keep said chromium in solution, forming saidcopper alloy material into a wire of an intermediate gauge, aging saidcopper alloy material wire to obtain submicron size for precipitatedchromium particles, and forming said copper alloy material wire to awire having a finish gauge optionally followed by a relief anneal toobtain desired tensile strength and elongation.

Other details of the copper alloys of the present invention, as well asother objects and advantages attendant thereto, are set forth in thefollowing detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In accordance with the present invention, there is provided two copperalloys which can be drawn into fine and ultra fine wires (wires having adiameter smaller than 0.010 inch).

In a first embodiment of the present invention, the copper alloycomprises from about 0.2 to 0.6 wt % chromium, preferably from 0.3 to0.5 wt % chromium, from 0.005 to 0.25 wt % silver, preferably from 0.05to 0.20 wt % silver, and the balance copper. The alloy may also containup to 0.015 wt % zirconium to further improve softening resistance. Whenpresent, zirconium is preferably added in an amount from 0.005 to 0.015wt %.

In a second embodiment of the present invention, the copper alloycomprises from about 0.2 to 0.6 wt % chromium, preferably from 0.3 to0.5 wt % chromium, from 0.01 to 0.12 wt % magnesium, preferably from0.05 to 0.1 wt % magnesium, and the balance copper. These alloys mayalso contain up to 0.015 wt % zirconium to further improve softeningresistance. When present, zirconium is preferably added in an amountfrom 0.005 to 0.015 wt %.

The alloys of the present invention may be cast using any suitablecontinuous or non-continuous casting technique known in the art.Following casting, the alloy may be processed into wire having aconvenient diameter. This processing may include a high temperaturesolution treatment to solutionize all or the majority of the chromiumfollowed by a rapid quench (such as in water) to keep the chromium insolution. This processing is important in order to be able to properlyutilize the chromium. Large particles (5-10 micron or larger) remainingfollowing the solution treatment are the harmful ones which will causewire breaks when drawing to fine and ultra fine diameters. A solutiontreatment temperature which may be used is from 925 to 1000 degreesCentigrade (from 1700 to 1830 degrees Fahrenheit) for 5 minutes to 5hours. A preferred solution treatment dissolves most or all chromiumparticles. After the solution treatment and the rapid quench, the copperalloy may then be drawn to an intermediate gauge wire, typically from0.036 to 0.064 inches in diameter, using any suitable drawing techniqueknown in the art. After being drawn to a wire of an intermediate gauge,the copper alloy wire is aged to obtain sub-micron size for theprecipitated chromium particles. A heat treatment temperature which maybe used at this point for aging is typically from 450 to 565 degreesCentigrade (from 850 to 1050 degrees Fahrenheit) for 1 to 5 hours. Thecopper alloy wire may then be drawn to a finish single end size, usingany suitable drawing technique known in the art, followed by a heattreatment to obtain the required tensile strength and elongation.Desired tensile strength is greater than 60 ksi and desired elongationis greater than 6-8%. The heat treatment is performed at a temperaturein the range of from 350 to 510 degrees Centigrade (from 650 to 950degrees Fahrenheit) for about 1 to 5 hours.

The wire formed from the copper alloys of the present invention may beused in round (drawn) or flat (rolled) shape. The wire may be used as asingle end wire or constructions made therefrom such as stranded as amulti-end wire, rope, bobbin, etc.

It is apparent that there has been provided in accordance with thepresent invention two copper alloys which fully satisfy the objectives,means, and advantages set forth hereinbefore. Other unforeseenalternatives, modifications, and variations may become apparent to thoseskilled in the art having read the foregoing description. Accordingly,it is intended to embrace those alternatives, modifications, andvariations which fall within the broad scope of the appended claims.

1. A copper alloy consisting essentially of from 0.2 to 0.6 wt %chromium, from 0.005 to 0.25 wt % silver, up to 0.015 wt % zirconium,and the balance copper.
 2. The copper alloy of claim 1, wherein saidchromium is present in an amount from 0.3 to 0.5 wt %.
 3. The copperalloy of claim 1, wherein said silver is present in an amount from 0.05to 0.20 wt %.
 4. The copper alloy of claim 1, wherein said zirconium ispresent in an amount from 0.005 to 0.015 wt %.
 5. A copper alloyconsisting essential of from 0.2 to 0.6 wt % chromium, from 0.01 to 0.12magnesium, up to 0.015 wt % zirconium, and the balance copper.
 6. Thecopper alloy of claim 5, wherein said chromium is present in an amountfrom 0.3 to 0.5 wt %.
 7. The copper alloy of claim 5, wherein saidmagnesium is present in an amount from 0.05 to 0.1 wt %.
 8. The copperalloy of claim 5, wherein said zirconium is present in an amount from0.005 to 0.015 wt %.
 9. A wire formed from a copper alloy consistingessentially of from 0.2 to 0.6 wt % chromium, from 0.005 to 0.25 wt %silver, up to 0.015 wt % zirconium, and the balance copper, and saidwire having a diameter less than 0.010 inches.
 10. The wire of claim 9,wherein said chromium is present in an amount from 0.3 to 0.5 wt %. 11.The wire of claim 9, wherein said silver is present in an amount from0.05 to 0.20 wt %.
 12. The wire of claim 9, wherein said zirconium ispresent in an amount from 0.005 to 0.015 wt %.
 13. A wire formed from acopper alloy consisting essentially of from 0.2 to 0.6 wt % chromium,from 0.01 to 0.12 wt % magnesium, up to 0.015 wt % zirconium, and thebalance copper, and said wire having a diameter less than 0.010 inches.14. The wire of claim 13, wherein said chromium is present in an amountfrom 0.3 to 0.5 wt %.
 15. The wire of claim 13, wherein said magnesiumis present in an amount from 0.05 to 0.10 wt %.
 16. The wire of claim13, wherein said zirconium is present in an amount from 0.005 to 0.015wt %.
 17. A process of manufacturing a copper alloy wire comprising thesteps of: providing a copper alloy material containing chromium;subjecting said copper alloy material to a solutionizing treatment tosolutionize a majority of said chromium; rapidly quenching said copperalloy material after said solutionizing treatment to keep said chromiumin solution; forming said copper alloy material into a wire of anintermediate gauge; aging said copper alloy material wire to obtainsubmicron size for precipitated chromium particles; and forming saidcopper alloy material wire to a wire having a finish gauge.
 18. Theprocess of claim 17, wherein said copper alloy material providing stepcomprises providing a material consisting of from 0.2 to 0.6 wt %chromium, from 0.005 to 0.25 wt % silver, up to 0.015 wt % zirconium,and the balance copper.
 19. The process of claim 17, wherein said copperalloy material providing step comprises providing a material consistingof from 0.2 to 0.6 wt % chromium, from 0.01 to 0.12 wt % magnesium, upto 0.015 wt % zirconium, and the balance copper.
 20. The process ofclaim 17, wherein said solutionizing step comprises subjecting saidcopper alloy material to a temperature in the range of from 925 to 1000°C.
 21. The process of claim 17, wherein said step of forming saidmaterial into a wire of intermediate gauge comprises drawing saidmaterial into a wire having a diameter in the range of from 0.036 to0.064 inches.
 22. The process of claim 17, wherein said aging stepcomprising subjecting said wire to a temperature in the range of from450 to 565° C.
 23. The process of claim 17, wherein said step of formingsaid wire into a finish gauge comprises drawing said wire to a wirehaving a diameter less than 0.010 in.
 24. The process of claim 17,further comprising subjecting said wire at finish gauge to an additionalheat treatment at a temperature in the range of from 350 to 510° C.